The present invention relates to an optical device designed as a molded package with a hybrid-packaging of a plurality of components such as optical components and semiconductor elements on a lead frame. The present invention also relates to a method of manufacturing such an optical device.
Heretofore, various optical devices and their peripheral components have been devised and developed for optical communication. A typical conventional optical device has two external terminals where one is for electrical signals and the other is for optical signals and a plurality of inner components such as optical components and semiconductor elements. The optical components include a photodiode (PD), a laser diode (LD), a planar lightwave circuit (PLC) board, an optical fiber, and so on, while the semiconductor elements include a preliminary amplifier for driving the LD and so on.
As an example of packaging, the optical device can be designed as a ceramic-packaged structure where the above components are housed in a ceramic housing and covered with a lid formed from metal, glass, ceramic or the like, or encapsulated with a resin.
FIG. 22 is a top view of a ceramic-packaged structure of one of the conventional optical devices. In the figure, the optical device 100 comprises a ceramic-package 111 in which optical components and the like are housed, a plurality of external terminals heads) 112, an optical fiber cord 113 protruded through the side of the package 111, and a plug connector 114 provided on the tip of the optical fiber cord 113.
However, the problem is that such a structure of the conventional optical device is not suitable for mass production in automated facilities because of the optical fiber cord 113 protruding through the side of the ceramic package 111. By the same token, there is another problem that high density mounting cannot be attained because of the following reasons. That is, the above structure of the conventional optical device is not suitable for a reflow-packaging, so that it is generally provided as of a dual inline package (DIP) type and mounted on a circuit board by inserting its external terminals or the like therein.
To solve the above problems, several approaches have been proposed so far to develop an optical device of the type that can be prepared by connecting an optical fiber cord to a package after mounting the package on a circuit board for input/output of optical signals. This kind of the structure can be seen in FIG. 23.
FIG. 23 is a top view of the conventional optical device having such a ceramic-packaged structure of the conventional optical device. In addition to the components shown in FIG. 22, the optical device further comprises a ferrule 121 and a receptacle 122. The ferrule 121 is optically coupled to the inner optical components and protruded from the package. The receptacle is responsible for holding an optical fiber cable to ensure an optical coupling between the optical fiber cable and the ferrule. By the way, it is noted that other parts are the same or like parts as those of FIG. 22, so that they have the same reference characters as those in FIG. 22.
The configuration of the optical device shown in FIG. 23 enables automation of its manufacturing system because a plug connector of an optical fiber (not shown) can be coupled to the receptacle 122 after mounting the package 111 on a circuit board. Therefore, it becomes possible to mount the optical device on the board by means of a re-flowing system.
In this case, however, the optical device is constructed as a ceramic packaged structure, so that there are some problems that the number of components is considerable and the manufacturing process is of high complexity. In addition, ceramic itself is expensive, so that the cost of manufacturing becomes high.
To solve the above problems, an optical device with a molded package in which inner components such as optical components and semiconductor elements are housed in a package and encapsulated with a molding resin by means of a transfer-molding technology has been proposed and developed so far.
FIG. 24 is a top view for illustrating a molded-package structure of the conventional optical device. FIG. 25 is a top view for illustrating a configuration of the optical device shown in FIG. 24, from which a receptacle is being detached. FIG. 26 is a cross-sectional view of the prime constituents of the optical device along the line XXVIxe2x80x94XXVI in FIG. 25. In this case, the conventional optical fiber further comprises a ferrule-mounting portion 131 of a lead frame, a plurality of external lead terminals 132 protruded from both longitudinal sides of the lead frame, a ferrule 133 mounted on the ferrule-mounting portion 131, an optical fiber 134 having one end portion on which the ferrule 133 is coaxially provided, an adhesive by which the ferrule 133 is bonded to the surface of the ferrule-mounting portion 131, and a molding resin 136 that forms a receptacle-inserting guide, a receptacle-securing-portion, and so on. In addition, the reference numeral 137 denotes a receptacle and 138 denotes a split sleeve. A receptacle-inserting guide, a receptacle-fixing portion and so on for mounting the receptacle 137 are formed using a molding resin.
In such a conventional optical device, the lead frame and ferrule 133 are encapsulated with the molding resin 136 by means of transfer molding technique, where one end 133a of the ferrule 133 is externally protruded from the molding resin 136. In addition, the ferrule 133 is placed on a flat surface of the ferrule-mounting portion 131.
We are now going to explain the details of the process for manufacturing the conventional optical device.
To begin with, a lead frame with a plurality of the same patterns connected to each other is formed as shown in FIG. 27. One of such patterns in the lead frame of FIG. 27 is illustrated as an enlarged view in FIG. 28. In the figure, the reference numeral 141 denotes a die pad, 142 denotes an inner lead, 143 denotes a dam bar, 144 denotes an outer frame portion, and 145 denotes a positioning hole. In addition, other components are the same or like components as those of FIGS. 25 and 26, so that they have the same reference characters as those of FIGS. 25 and 26.
Subsequently, the lead frame is subjected to a depressing process (or alternatively referred as a sinking process) by which areas indicated by xe2x80x9cP1xe2x80x9d, xe2x80x9cP2xe2x80x9d, xe2x80x9cP3xe2x80x9d and xe2x80x9cP4xe2x80x9d in FIG. 28 are bent into a predetermined angle to lower the die pad 141, and then each component is mounted on the lead frame.
After that, the lead frame is placed on a lower die having positioning pins. The pins are inserted into the positioning holes 145 on the lead frame to make sure that the lead frame is in the right place. Subsequently, an upper die is mated with the lower die to sandwich the lead frame between them. FIG. 29 is a side view of such a configuration shown in the direction of the arrow xe2x80x9cXxe2x80x9d in FIG. 25. In the figure, the reference numeral 146 denotes the upper die and 147 denotes the lower die. The upper die 146 and the lower die 147 have their own recesses. The recesses are symmetric with respect to the mating surface between them and each recess has a semicircle cross-sectional profile in the direction of the radius thereof. Thus, the recesses form a cylindrical-shaped opening when the upper and lower dies 146, 147 are mated to each other. In addition, the opening has a slightly larger diameter than that of a ferrule 133 to leave a clearance of about 20 micrometers when the ferrule 133 is coaxially placed in the opening. Other components are the same or like components as those of FIG. 25 and FIG. 26, so that they have the same reference characters as those of these figures.
Subsequently, a molten molding resin is injected into a cavity formed between the upper die 146 and the lower die 147 and then cured within a fixed time period, followed by cutting the lead frame at predetermined positions to separate individual optical devices.
In the configuration of the conventional molded package, as described above, the ferrule 133 is positioned on a flat surface of the ferrule-mounting portion 131. Thus, it is difficult to make a correct positioning of the ferrule 133, so that the ferrule 133 cannot be provided in the right place relative to the positioning holes 145 of the lead frame. Consequently, as shown in FIG. 30, there is a problem that the ferrule 133 suffers any damage as a result of the interference between the ferrule 133 and the upper and lower dies 146, 147.
In addition, there is another possibility that the upper die 146 and the lower die 147 may be not in the right place. In this case, as shown FIG. 31, there is a problem that the ferrule 133 suffers any damage as a result of the interference between the ferrule 133 and the upper and lower dies 146, 147.
Furthermore, the lead frame is subjected to the depressing process, so that the variations in the levels of the depressed die pad 141. As a result, there are the possibilities of troubles in optical coupling and so on to be caused by detaching ferrule 133 from the ferrule-mounting portion 131, damaging the optical fiber 134, warping the die pad 141, or the like.
For solving the above problems, there is an idea of shaping the upper and lower dies so as to allow the misalignment of the ferrule 133 and the misalignment of the mating between the upper and lower dies 146, 147. In this case, however, the molding resin will be leaked from the space between the ferrule 133 and the upper and lower dies 146, 147. As a result, the accuracies of outer dimensions of the ferrule 133 will be dropped. Therefore, such a shape cannot be applied on the upper and lower dies 146, 147.
Incidentally, JP-A-10-227952/1998 discloses an optical device having a ferrule-mounting portion which is formed as a upwardly opened structural member in the form of the letter xe2x80x9cUxe2x80x9d in cross section for the purpose of the positioning of the ferrule. FIG. 32 illustrates a perspective diagram of the conventional optical device disclosed in JP-A-10-227952/1998. In the figure, the reference numeral 151 denotes a lead frame, 152 denotes a ferrule, 153 denotes an optical fiber, 154 denotes a silicon substrate, 155 denotes an optical component, 156 denotes a push plate for holding an optical fiber, and 157 denotes a molding resin. In the lead frame 151, furthermore, the reference numeral 158 denotes a die pad, 159 denotes a ferrule-mounting portion, and 160 denotes a lead.
Regarding such a conventional optical device, the positioning of the ferrule 152 is attained by mounting the ferrule 152 on the upwardly-opened xe2x80x9cUxe2x80x9d-shaped ferrule-mounting portion. For automatically mounting the ferrule 152, there is a need to create clearance between an inner surface of the xe2x80x9cUxe2x80x9d-shaped ferrule-mounting portion and an outer peripheral surface of the ferrule 152. In addition, the ferrule-mounting portion 159 may be deviated from the right position with reference to positioning holes on the lead frame. Therefore, such a conventional optical device cannot allow the positioning of the ferrule with very high precision.
The present invention is implemented to solve the foregoing problems. It is therefore an object of the present invention to provide an optical device and a method for manufacturing the optical device, where damage to a ferrule due to interference between the ferrule and the upper and lower dies is minimized.
It is another object of the present invention to provide an optical device and a method for manufacturing the optical device, where attachment of a ferrule to a ferrule-mounting portion is improved, damage to an optical fiber is minimized, and obstruction to an optical coupling is minimized.
According to a first aspect of the invention, there is provide an optical device having a molded-package structure, comprising: a lead frame having a ferrule-mounting portion; a ferrule mounted on the ferrule-mounting portion; and a molding resin that encapsulates the lead frame and the ferrule by means of a transfer-molding technique except that an end of the ferrule protrudes through the surface of-the molding resin to the outside, wherein a first groove parallel to a longitudinal axis of the ferrule is formed on the ferrule-mounting portion and the ferrule is placed on the first groove.
Here, at least one second groove perpendicular to the first groove may be formed on the ferrule-mounting portion.
At least one second groove perpendicular to the first groove is formed on the ferrule-mounting portion and a filler made of a resin may be provided on a gap between the ferrule and the ferrule-mounting portion.
In a second aspect of the present invention, there is provided an optical device having a molded-package structure, comprising: a lead frame having a ferrule-mounting portion; a ferrule mounted on the ferrule-mounting portion; and a molding resin that encapsulates the lead frame and the ferrule by means of a transfer-molding technique except that an end of the ferrule protrudes through the surface of the molding resin to the outside and an end of the ferrule-mounting portion protrudes through the surface of the molding resin to the outside.
Here, a first groove parallel to a longitudinal axis of the ferrule may be formed on the ferrule-mounting portion and the ferrule may be placed on the first groove.
A first groove parallel to a longitudinal axis of the ferrule may be formed on the ferrule-mounting portion and the ferrule is placed on the first groove, and also at least one second groove perpendicular to the first groove may be formed on the ferrule-mounting portion.
A first groove parallel to a longitudinal axis of the ferrule may be formed on the ferrule-mounting portion and the ferrule may be placed on the first groove, at least one second groove perpendicular to the first groove is formed on the ferrule-mounting portion, and a filler made of a resin is provided on a gap between the ferrule and the ferrule-mounting portion.
Here, the optical device may further comprise a ferrule-mounting member on the ferrule-mounting portion, where the ferrule-mounting member has a concave top surface on which the ferrule is disposed.
In a third aspect of the present invention, there is provided an optical device having a molded-package structure, comprising: a lead frame having a ferrule-mounting portion, a die pad, at least one inner lead, and at least one outer lead; a ferrule mounted on the ferrule-mounting portion; and a molding resin that encapsulates the lead frame and the ferrule by means of a transfer-molding technique except that an end of the ferrule protrudes through the surface of the molding resin to the outside, wherein the die pad and the inner lead are in the same plane.
Here, the optical device may further comprise a recessed portion that extends from the underside of the molding resin to the underside of the die pad, where the recessed portion may be formed at the time of molding using dies.
The optical device may further comprise a recessed portion that extends from the underside of the molding resin to the underside of the die pad, where the recessed portion may be formed at the time of molding using dies and encapsulated with an encapsulating member.
In a fourth aspect of the present invention, there is provided a method for manufacturing an optical device that includes a lead frame having a ferrule-mounting portion, a ferrule mounted on the ferrule-mounting portion, and a molding resin that encapsulates the lead frame and the ferrule by means of a transfer-molding technique except that an end of the ferrule protrudes through the surface of the molding resin to the outside, comprising the steps of: disposing the lead frame on a lower die, where the lead frame has the ferrule-mounting portion on which the ferrule is mounted; and mating the lower die with an upper die to sandwich the lead frame between the upper die and the lower die, wherein one of the upper die and the lower die has a recessed surface facing to the ferrule-mounting side of the ferrule-mounting portion and the other has a flat surface facing to the opposite side of the ferrule-mounting portion, where the recessed surface has a U-shaped recess on which the ferrule is disposed.
In a fifth aspect of the invention, there is provided a method for manufacturing an optical device that includes a lead frame having a ferrule-mounting portion, a ferrule mounted on the ferrule-mounting portion, and a molding resin that encapsulates the lead frame and the ferrule by means of a transfer-molding technique except that an end of the ferrule and an end of the ferrule-mounting portion protrude through the surface of the molding resin to the outside, comprising the steps of: attaching a block member having a cavity for holding the ferrule around the ferrule from one end of the ferrule; placing the lead frame on a lower die, where the lead frame has the ferrule-mounting portion on which the ferrule attached to the block is mounted; and mating the lower die with an upper die to sandwich the lead frame between the upper die and the lower die, wherein the block member has an end face that faces to the ferrule and defines an external shape of the molding resin.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in consideration with the accompanying drawings.